1. Field of the Invention
The present invention relates generally to devices for detecting intermediate points within wells, gas and oil pipelines, and the like, and more specifically to a system using radio frequency resonant devices installed at various points in the well or pipe. A detector is inserted into the pipe, and detects the resonant devices where installed to transmit location or depth and other information back to a station at the surface or along the pipe. The present invention may provide for the storage of the information gathered for downloading upon retrieval of the device from the well or pipe.
2. Description of the Related Art
The need for accurate measurement of the depth of a drilled well is critical, as oftentimes the stratum of interest in the well, resides within a relatively narrow band. Wells are typically cased after drilling, with cement being poured between the casing and the wall of the drilled hole in order to seal and stabilize the hole. The casing and cement are perforated at the desired depth in order to access the stratum of interest (oil bearing deposits, gas, water, etc.), with the casing and cement serving to prevent the flow and mixing of undesired fluids with the fluid of interest from the well (e.g., water with oil, etc.).
In view of the above, it is critical that the well be perforated at precisely the proper depth in order to avoid drawing an undesirable fluid into the well, and/or missing the desired stratum of interest in the well. As wells typically extend from a few to several thousand feet below the surface in the case of oil and gas wells, the precise measurement of the depth of the well to within a few feet, poses a difficult problem. U.S. Pat. No. 5,279,366 provides an excellent and detailed discussion of the problem in the Background of the Invention, columns 1 through 4, for further background.
Accordingly, numerous devices and systems have been developed in the past for logging or measuring the precise depth of the well, for perforating the well or for other purposes as required. Such principles as MRI (magnetic resonance imaging), gamma ray detection, and others, have been utilized in order to enable a detector lowered into the well casing to determine its position or depth within the hole. However, none of the systems or principles utilized in the past, provide the needed accuracy to enable an operator to determine precisely the depth of the tool within the hole. It is very easy for the well to be logged incorrectly, or for the tool to detect the wrong joint or point in the casing, and thus throw off all calculations and measurements accordingly. As the conventional well casing pipe has a length of some thirty feet, it will be seen that an error in the detection of one joint location, could cause a perforating gun or other tool to miss the stratum of interest completely.
Those skilled in the art are aware that the limitations of the prior art extend to other types of pipelines and the like, and are not limited only to generally vertical well bores. For example, the standard procedure for examining a cross-country oil, gas, or other pipeline, is to "pig" the line, i.e., send a mechanical device (called a "pig") through the line, generally by pneumatic means. The "pig" may sense various information relating to the condition of the line, or other factors, which information may be stored within the device until it is recovered at some point in the line. However, any flaws or other problems in the line must be identified as to location, and the mechanical "pigs" used for such operations have no means of determining their position in the line. Rather, their location must be detected externally, by a worker stationed along the pipe or line as the "pig" travels through the line, and who logs the passage of the "pig" at various points along the line, relative to time. By knowing the time that any information was gathered in the pipe, and the time of passage of the "pig" at various points, the location of any anomalies may be indirectly determined.
However, it will be seen that it can be difficult to determine the precise location of various anomalies or other points of interest in such a pipeline, as the detection of the passage of the "pig" through the line, is determined at only a relatively few widely separated points along the line. Thus, when the record of the recovered "pig" is examined, it may not be possible to narrow the location of some point of interest in the line, to an area smaller than perhaps a few hundred feet of pipeline, or perhaps more.
Accordingly, a need will be seen for a system which positively identifies the location or depth of a well tool at various points within the well. The system comprises a plurality of passive or active radio frequency resonant devices, which are installed at several, or all, of the joints in the well casing. Each of the devices is preferably constructed or tuned to provide a unique individual signal. A well tool is provided which transmits a low power and/or directional signal on an appropriate frequency for reception by the devices, which then resonate to provide a responding signal to the well tool. The responding signal passes up the wire line to the well operator at the surface, who is able to determine precisely the location or depth of the well tool in the well. Alternatively, the information may be stored within the downhole tool, for downloading into a computer or other suitable reading device at the surface, after recovery of the tool.
A further need will be seen for a system which is capable of positively identifying the location of a tool which is passed through a pipeline or the like, and recording the location corresponding to the tool at various points in time as the tool passes through the pipeline. The system may utilize active or passive radio frequency resonant devices, with information being stored within the pipeline tool for later recovery when the tool is recovered from the line.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 4,572,293 issued on Feb. 25, 1986 to James G. Wilson et al., titled "Method Of Placing Magnetic Markers On Collarless Cased Wellbores," describes the magnetic polarizing of well casing by positioning one or more electromagnets within the casing, and activating the electromagnets to impart a permanent magnetic field at the location of the electromagnet(s) within the casing or pipe. The magnetically polarized area may be detected using a conventional magnetic reading casing collar locator. The Wilson et al. method does not provide any means of differentiating between magnetically marked spots, nor of precisely positioning the magnetically polarized areas at predetermined points in the casing. Moreover, Wilson et al. do not disclose any means of logging or determining the position of a device in a cross country or other fluid pipeline, as provided by the present method and apparatus.
U.S. Pat. No. 4,630,044 issued on Dec. 16, 1986 to Rudolf Polzer, titled "Programmable Inductively Coupled Transponder," describes a passive radio identification device (PRID) including a memory for modulating the response signal when triggered by an appropriate transmitter. Polzer describes the placement of the resonating transponder on a moving object, e.g., a railroad car, with the triggering transmitter having a stationary mounting. This configuration is precisely the opposite of the present invention, with its stationary responding devices and triggering transmitter being mounted within a moving well hole or pipeline "pigging" tool. Moreover, Polzer makes no suggestion of using his invention for determining depth or other characteristics in a well casing or other fluid pipeline, as provided by the present invention.
U.S. Pat. No. 4,808,925 issued on Feb. 28, 1989 to Gary K. Baird, titled "Three Magnet Casing Collar Locator," describes a magnetic device for detecting pipe or casing joints in a well. The device provides a specially shaped toroidal magnetic field, which magnetically affects the ferrometallic casing and casing joints. A detector associated with the device detects variations in the magnetic field as the field changes as it passes each casing joint. Baird makes no provision for detecting any differences in the joints. Rather, each joint appears essentially the same when detected, and the operator cannot determine precisely where in the casing the device is located. Each joint must be counted in order for the location to be determined, and no other information is provided by the Baird device. Baird does not disclose any means of logging or determining the precise location of a pigging tool in a cross country or other than vertical fluid pipeline, as provided by the present invention.
U.S. Pat. No. 5,279,366 issued on Jan. 18, 1994 to Patrick L. Scholes, titled "Method For Wireline Operation Depth Control In Cased Wells," describes the use of both magnetic and radioactive location markers in a well casing. The detector device is capable of detecting both high energy radiation (gamma rays) and magnetic anomalies, thus making it easier to confirm that: well depth logs using either system separately; are properly "tied in." The Scholes '366 U.S. Patent provides an excellent explanation of the problem of well depth control and logging, as well as the importance of a solution for the problem, in the Background of the Invention portion of the disclosure, as noted further above. However, Scholes does not provide any means of differentiating between different joints or other locations along the length of the casing, nor any radio frequency resonant means for doing so. Moreover, Scholes is silent regarding any form of logging or determining the position of a tool in other than a vertical line, whereas the present system may be applied to any fluid line in a generally vertical or other than vertical orientation.
U.S. Pat. No. 5,361,838 issued on Nov. 8, 1994 to Marion D. Kilgore, titled "Slick Line Casing And Tubing Joint Locator Apparatus And Associated Methods," describes a device which is usable with a slick line, i.e., a monofilament metal or other line which does not carry an electrical signal. The device relies upon an integral magnetic anomaly detector for detecting pipe or casing joints. When a joint is detected, the device drives a drag producing structure against the inner surface of the casing, with the drag registering as a momentary increase in tension on the line at the surface as the device passes the joint. Thus, the Kilgore device can only be used when being drawn upwardly through the pipe, and does not utilize any radio frequency resonance means. The Kilgore device is also unworkable in other than a generally vertical line, whereas the present system is operable in any fluid line, regardless of its orientation.
U.S. Pat. No. 5,457,447 issued on Oct. 10, 1995 to Sanjar Ghaem et al., titled "Portable Power Source And RF Tag Utilizing Same," describes a radio frequency (RF) device providing an interrogation signal and receiving a response from the interrogation signal. The device may be powered by any one or more of several electrical sources, including conventional battery power, solar or infrared cells, etc. However, Ghaem et al. are silent regarding a responding unit for their RF tag device. While the present invention makes use of an RF transmitter and receiver disposed within a well downhole tool, pipeline pigging tool, or the like, the present invention also makes use of inert or active resonant responding devices which are triggered by the RF transponder device of the well or pipeline tool, which resonant responding devices are not a part of the Ghaem et al. disclosure.
U.S. Pat. No. 5,497,140 issued on Mar. 5, 1996 to John R. Tuttle, titled "Electrically Powered Postage Stamp Or Mailing Or Shipping Label Operative With Radio Frequency (RF) Communication," describes a small and very thin radio receiver and transmitter, including a memory chip for modulating the transmitted signal to provide certain specific information, e.g., routing, etc. The Tuttle disclosure provides for a thin, flat battery for power of the device, and accordingly includes "sleep" and "wake" circuitry which is triggered by a transmission from another device. The present invention does not require any integral electrical power in the specific form of an electric battery, but resonates when power is received from a nearby transmitter. The present device may include active circuitry requiring electrical power, but the electrical power is generated by electrochemical means using the fluid within the well or pipe, as an electrolyte. The Tuttle device is not a resonant device.
U.S. Pat. No. 5,626,192 issued on May 6, 1997 to Michael L. Connell et al., titled "Coiled Tubing Joint Locator And Methods," describes a tube which is lowered into the well pipe string for locating pipe joints. The device includes a fluid passage formed generally axially therethrough, and an electromagnetic joint detector which senses the increased mass of each joint, according to the disclosure. When a joint is detected, a lateral valve is opened, which decreases the fluid flow resistance through the device and produces a pressure drop which is transmitted to the surface. The Connell et al. device can only sense each joint, and cannot detect any difference between different joints, whereas the present device may provide means for differentiating between different joints in the well casing or fluid pipeline.
U.S. Pat. No. 5,720,345 issued on Feb. 24, 1998 to Timothy M. Price et al., titled "Casing Joint Detector," describes a magnetic anomaly detector which detects the variations in magnetic flux across pipe or casing joints, as in other devices of the prior art discussed further above. The detector may also measure the distance traveled down the borehole, and correlate this distance with the number of joints passed. However, Price et al. make no provision for distinguishing between different casing or pipe joints, for determining precisely which joint is being passed at any given point. Also, as with other magnetic anomaly detectors, the device must be moving at some minimum velocity through the casing in order to generate the spike in electromagnetic energy for generating a detection signal. The present active or passive RF system is operable at any practicable velocity in vertical, horizontal, or otherwise oriented fluid pipelines of virtually any type, i.e., ferromagnetic or other material.
European Patent Publication No. 013,494 published on Jul. 23, 1980 to British Gas Corporation, titled "Measurement Of Velocity And/Or Distance," describes a device which produces a magnetic anomaly in the wall of a ferrometallic pipe, and then detects the anomaly as the device passes. The device may thus measure its velocity through the pipe, by measuring the time between the production of the magnetic anomaly and its detection by another part of the device, with the distance between the two components being known. As in other devices using magnetic principles or means discussed further above, the British Gas device cannot distinguish between different magnetic anomalies produced thereby, but can only count the total number of magnetic anomalies along the length of the pipe and provide a distance measurement based upon the distance between the magnetic anomaly producer and detector. No RF means, nor use in other than a generally vertical downhole, is disclosed in the British Gas Corporation patent publication.
European Patent Publication No. 412,535 published on May 11, 1994 to Michael L. Smith, titled "Tubing Collar Position Sensing Apparatus, And Associated Methods, For Use With A Snubbing Unit," describes a device for electromagnetically detecting tubing or joint collars for progressively opening and closing the blowout pressure seals of a blowout valve. Accordingly, there is no need, and no teaching, of any means for distinguishing between different joints along the length of the tube or pipe. Smith notes that the measurement of the pipes cannot be accomplished by odometer means alone, due to slight variations in pipe length and in the length of engaged threads at each coupling, to which problem the present invention responds. Moreover, the present system is adaptable to both generally vertical well holes, as well as generally horizontal or other orientation gas and other fluid lines.
European Patent Publication No. 651,132 published on May 3, 1995 to the Halliburton Company, titled "Method For Locating Tubular Joints In A Well," describes a device which applies lateral pressure to the walls of the pipe whenever a joint is detected. The increased drag of the device increases the tension on the line as the device is raised up the pipe, thus enabling the joints to be detected without requirement for an electrical connection between the device in the pipe and the surface. The device described in the '132 European Patent Publication is the same as that described in the '838 U.S. Patent, and discussed further above. The same differences and distinctions noted in the above discussion, are also seen to apply here.
Finally, European Patent Publication No. 730,083 published on Sep. 4, 1996 to the Halliburton Company, titled "Method And Apparatus For Use In Setting Barrier Member In Well," describes a device using conventional magnetic anomaly detection means for detecting pipe or casing joints, for positioning a barrier within the pipe or casing so that the barrier is not positioned on the joint. There is no need, and no teaching, for the device to distinguish between different joints, as all that is necessary for the Halliburton device is to determine that the barrier or seal will not be positioned directly on a joint.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.